Structures and rheological properties of organo-sepiolite in oil-based drilling fluids

This work reports the characterization of organo-sepiolite (OSep) and the evaluation of the rheological properties of OSep in oil-based drilling fluids. Sepiolite was modified with benzyl dimethyl octadecyl ammonium chloride and OSep samples were prepared. X-ray diffraction, scanning electron microscope, specific surface area and thermal analysis were applied to characterize the structure of OSep. Viscosity, yield point, dynamic rheological behavior and thixotropy were used to appraise the Theological properties of OSep/oil fluids aged at different temperatures. Surfactants coat on the surface of Sep and insert into the channels and tunnels, resulting in lipophilicity and decline of surface area of OSep. Individual fibers, crystal bundles and small particles of OSep form big particles with smooth surface after organic modification. Rheological properties of OSep/oil fluids can be promoted by the increase of surfactants while extremely high surfactant's loading level results in decrease of rheological properties. OSep modified with 35% of surfactant shows the best rheological properties. Temperature rising promotes the rheological properties of OSep/oil fluids by changing the organizations of OSep. However, extremely high temperatures result in deterioration of rheological properties. OSep is a potential rheological additive in oil-based drilling fluids with excellent rheological properties.